许杰友 Jieyou Xu (Joe) 7112951caa Rollup merge of #138303 - DiuDiu777:rc-fix, r=Mark-Simulacrum ... Fix Ptr inconsistency in {Rc,Arc} ### PR Description This pr aims to address the problem discussed on [zulip](504259637). ### Problem Clarification As this post presents, the `{Rc, Arc}::{in/de-crement_strong_count_/in}` do not limit the layout of the memory that `ptr` points to, while internally `Rc::from_raw_in` is called directly. UB doesn't just appear when the strong count is decremented to zero. Miri also detects the UB of `out-of-bounds pointer use` when increment strong count is called on a pointer with an incorrect layout(shown as below). ```rust use std::rc::Rc; #[repr(align(8))] struct Aligned8(u64); #[repr(align(16))] struct Aligned16(u64); fn main() { let rc: Rc<Aligned8> = Rc::new(Aligned8(42)); let raw_ptr = Rc::into_raw(rc); unsafe { Rc::increment_strong_count(raw_ptr as *const Aligned16); } } ``` Miri output: ``` error: Undefined Behavior: out-of-bounds pointer use: expected a pointer to 32 bytes of memory, but got alloc954 which is only 24 bytes from the end of the allocation ```		2025-03-16 09:40:06 +08:00
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src	Rollup merge of #138303 - DiuDiu777:rc-fix, r=Mark-Simulacrum	2025-03-16 09:40:06 +08:00
Cargo.toml	Migrate alloc to Rust 2024	2025-03-11 09:46:34 -07:00